When paper such as ledger or magazine paper is recycled by first breaking the paper down into a pulp slurry containing its individual components, long cellulose fibers are recovered that are useful for making tissue or other paper products. The slurry also contains a significant amount of other materials including primarily kaolin clay and short cellulose fibers which are not useful for making tissue. In an effort to make use of the maximum amount of these other materials, various products have been developed. For example, such materials have been used to make various absorbent products including floor and other absorbents and cat litter.
Desirable characteristics for granular absorbent products include a high rate of absorption of liquids, a high bulk density, and a high resistance to attrition. For example, U.S. Pat. No. 4,343,751 (the '751 patent) discloses pellets that may be impregnated or coated with a variety of substances, including fertilizers, pesticides, odor reducing substances, and colorants to provide a variety of different absorbent products, including cat box filler, fertilizers, soil conditioners and floor absorbent. The '751 patent discloses the use of paper sludge in amounts between ten percent and fifty percent of the total mass of the agglomerated solids. However, the absorbency is less than ideal as seen in the examples which include pellets having 50% paper sludge and 50% clay fibers, a bulk density of 38 lbs/ft and only 78% absorbency (see Chart 2, sample 008).
Another example is disclosed in U.S. Pat. No. 5,019,564 (the '564 patent) which is directed to non-clay agricultural granules. The '564 patent discloses an agricultural granule capable of carrying and releasing incorporated biocidal or nutritional agricultural chemicals. The granule is formed by the agitative agglomeration of a plant fiber slurry and resembles a clay granule in all respects except for its chemical inertness. The '564 patent states:
At 10% fiber and below granule formation is very poor and produces a quantity of fine powder residue having between 87-88.6% ash. Attrition rates also increase as fiber content decreases, and at less than 10% fiber, granules were often too friable to obtain accurate attrition data. Finally, the percentage of fines (granules of less than 60 Mesh) obtained remained fairly constant from 100% fiber down to 40% and then increased markedly. Fines contained about 89.1% or almost entirely filler.
(Column 6, line 61 through column 7, line 2).
Clay products, such as those described in the '751 patent, have the disadvantage of low absorbency when mixed with paper sludge, and relatively high attrition rates when the fiber content is low, as described in the '564 patent. When used as a floor absorbent, it is desirable that the granules retain their integrity after absorbing water or oil from the floor.